In the paper, the high temperature plasticity of 15MnNbV was tested with MMS-200 thermal simulated test machine. The results showed that the reduction of area of 15MnNbV at 900 ℃ was only 26%, temperature of round billet entering straightening segment was about 900 ℃ during continuous casting, with the stress of straightening roll, there was easily to be microcracks on the surface of round billet, especially the Ф430 mm round billet causing wall scale on outside surface of steel tube. The composition of 15MnNbV was adjusted through analyzing the influencing factors for high temperature plasticity of steel and characteristics of precipitation for niobium and vanadium in steel. After that, the reduction of area of 15MnNbV at 900 ℃ reached 88%, surface quality of round billet was improved and wall scale on outside surface of steel tube was eliminated.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |